Nutrient Monitoring System


Excess nutrients, also known as eutrophication, can appear seasonally, after an upwelling of nutrient-rich water, or from human-introduced sources such as fertilizer runoff, feedlot waste, urban stormwater runoff and wastewater treatment plant discharge. Watersheds increasingly struggle to handle resulting nutrient loads and suffer adverse effects such as harmful algal blooms (HABs), red tides, fish kills, and decreased productivity. Better understanding of nutrient loads and mitigation can be achieved in part through automated, real-time monitoring systems.

Nutrient Monitoring

Nutrient overload has received more attention in recent years due to an increased occurrence of harmful algal blooms that have affected rivers, lakes, ponds and coastlines. Though algae are a critical component in aquatic food webs, under the right conditions they can become toxin-producing HABs that threaten ecosystems, drinking water supplies and even human health.
Over-application of fertilizers and other sources introduce unnaturally high nutrient concentrations, particularly nitrate and phosphorus, which feed algal growth.
Warmer water can accelerate the growth rate of cyanobacteria and allow them to out-compete other types of algae.
Cyanobacteria, often referred to as blue-green algae, perform photosynthesis and are the most common type of HABs in freshwater.
In coastal water, excessive algal growth can cause so-called “red tides” characterized by discoloration of the water in deep green, brown or even red hues.
Golden algae HABs are becoming a more common occurrence in rivers and lakes especially with higher salinity or mineral content and often result in fish kills.
Exposure to toxins produced by HABs can cause skin irritation, liver damage, respiratory issues and neurological damage in humans.

Typical Nutrient Monitoring System

An effective nutrient monitoring system should provide real-time measurement data not only at the body of water subject to harmful algal blooms, but also along tributaries that transport nutrients through the watershed when possible. By measuring at multiple locations, point sources can be located and predictive modeling can be developed to provide advanced warning when the conditions are right for HABs to propagate.

Nutrient monitoring networks may include both buoy-based and structure-mounted sensors. A typical system may consist of several mast-mounted NexSens X2 data logger dispersed throughout a watershed or concentrated closer to one location known to be susceptible to excess nutrient loads. The X2 transmits data wirelessly in real-time via radio, cellular or satellite communications to the WQData LIVE web datacenter, where data can be viewed and exported and alarms configured.

The most common sensor types deployed in nutrient monitoring networks are nitrate sensors such as the TriOS NICO UV nitrate sensor and blue-green algae sensors like those from YSI, Turner Designs, Eureka and In-Situ. Various other sensor types including weather stations, temperature profiling strings, underwater PAR sensors, dissolved oxygen (DO) and carbon dioxide sensors may be used in a nutrient monitoring network. All of these sensor types are compatible with the X2 data logger, which automatically detects sensors and facilitates data transfer to WQData LIVE.

Contact a NexSens Applications Engineer today to discuss your nutrient monitoring application.

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Case Studies


Lake Erie Tributary Monitoring

The western basin of Lake Erie gets a lot of attention thanks to its role in large algal blooms, but it is not the only part of the lake affected by nutrient runoff. There are organizations all around Lake Erie that work to manage runoff going into different basins of the lake. One of those is the Northeast Ohio Regional Sewer District, which maintains multiple water quality monitoring stations along creeks and rivers that flow into Lake Erie’s waters near Cleveland.

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Weir Installation Water Quality Effects

Because of its location in an agricultural watershed, a ditch in Minnesota’s Blue Earth County was retrofitted with a weir to help control discharges of excess nutrient and sediment loads. Curious to see what effects the new construction had on conditions downstream, researchers at Minnesota State University set out to investigate. They began with a set of baseline data gathered between the months of April and November in 2013. These touched on the stream’s temperature, pH and dissolved oxygen levels, which they found to be increasing in a correlated way significantly throughout the day.

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Florida Wetland Nutrient Transport

Officials at the South Florida Water Management District oversee many stormwater treatment areas as part of their mission to manage and protect water resources in southern Florida. Those include many constructed wetlands, some with aquatic vegetation and some without. Because the effects of aquatic vegetation on nutrient transport in wetlands are relatively unknown, scientists with the Management District set up monitoring equipment to learn more. Their investigation looks specifically at the role that wind plays in wetland nutrient transport, given the presence or absence of vegetation.

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